new power brake set up not working at all

after asking for a few ideas, i put a master/booster combo (all new) from a 68 chevelle, drum/drum car into my 60 Pontiac.

what would cause the pedal to go ALL the way to the floor,,,as in NO pedal at all when the booster is activated.

I bled the fronts out just fine,,,but did run into an issue at the rear,,,seems i'm not getting any fluid out back. now,,,i guess it's possible i've got a collapsed line which could have been there for some time,,, or the stroke isn't long enough to activate the rears, but wouldn't i still get at least some grab from the fronts????

this set up does have an adjustable rod in the booster which i had to bring out almost all the way to get it to contact the piston in the master cylinder (which is listed for power and manual use)

i hate brakes.

 

If the booster and MC are off the same car there should be not reason to have to adjust the booster to MC rod lenght. Did you bench bleed the MC ? The lack of fluid at the rear tells me you got that booster push rod toooooo long and the rear piston is not returning all the way. Not returning means the little ports that the fluid flows through are not opening to let fluid in the the rear bore that equals no fluid to the rear wheels.

 

try jacking the front of the car up high as you can get it and open the rear bleeders and let it gravity feed i had to do that on my dually once!!!and did you bench bleed the master cylinder before you put it in?

 

yes, i did bench bleed the master.

when i went to mate the booster to the master,,,the rod in the booster was about 3/4 of an inch from hitting the piston, so i ran it out so it just hit the piston in the master.

 

First I would check to make sure your getting fluid pressure out of both ports of the mc. Could just be alot of air in the back lines.

 

I have had good luck with the gravity bleed. The best way is a pressure bleed, but if you dont have the bleeder or access to one it won't help. If it has a proportioning valve, it may need to be reset. Sometimes the valve will move to one side only letting the front brakes get fluid.

Hope this helps,

Scott

 

no proportioning valve on this set up. drums all the way around.

 

Duh... I had to go back and read your original post. Sorry, have had the same problem due to the proportioning valve.

Scott

 

i will double check that, but even if i did have a lot of air in the lines,,,which i shouldn't as this was a running, stopping car, and only pulled the master and booster, shouldn't i still get some pedal feel from the fronts??? i'm beginning to wonder if my master might be bad???...whoa, that's some crazy S&M shit......

 

I know what the problem is on my 69 There is a valve underneath the mastercylinder You have to push the button on the back in,I had my dad hold it using a file.My friend pumping the brakes and me bleeding.The part is called a residual valve.Its covered by a black rubber cover.Let me know if that's the problem.I had the same problem When pushed lets fluid go to the rear cylinders or bad master cylinder

 

no such item on my master.

 

I stand by my first comment, if the booster AND MC were suspost to be a matched unit there is absolutly no reason to mess with the booster pushrod.

 

well,,the 2 units came separately. and both are used in dozens of different cars/years in different combos. if i hadn't brought the rod out,,,there would have been over a half an inch of free play between the piston and the rod. if the rod is only moving about an inch over all,,,i'm losing half the travel??? that doesn't seem right to me.

 

almost forgot,,,i DID try it with the rod in it's original location....and got even worse results than when i moved it out to meet the piston in the master.

 

I just replaced my master cylinder (CPP) it came with a pin that extended the plunger out to match the power booster brake pin so that no adjustment is needed or very little. Check out their web site they have instructions and pictures. Good luck.

Krruzer

 

Hmmm. I wonder if you're not getting enough travel. Perhaps an "extension" on the plunger is needed.

 

Still think you have mis-matched parts. Things HAVE been known to be misboxeded/id'ed.

 

i thought that as well, but i've looked up the part numbers and they all match. even went and got ANOTHER master. has a different cap, but same part number, and same deep bore piston.

i was able to get a bit better feel from it after putting it on and bleeding, but still goes all the way to the floor before stopping the car.

i'm wondering if my pedal ratio is messed up????

 

I think you could be on the right track Erik. YOu've got a non-power brake pedal pushing a power brake M/C now....I'm no expert, but you may want to try messing with the ratio. Perhaps the non-power brake pedal doesn't provide enough travel to fully engage the power brake system..

See if you can fashion a longer plunger and check if that makes a difference.

By the way, I'm jsut thinking out loud here, and I really don't know shit about shit, but it may be worth a try.

 

That is a very good question. Just might be your problem.

Usually people use the entire pedal/mounting bracket/ booster/ M/C from the original car because those Detroit engineers designed everything to work as a unit.

I hope you are using the pedal and it's mounting bracket that comes with that master cylinder and booster. If not, then I would suggest you check the mechanical design of the pedal ratio of that modern brake pedal, then modify your existing pedal assembly to match.

 

the car was originally a power brake car.

however, i did remove the bracket for the new booster, as it was one of those angle mount ones, but i still spaced it out about 2 inches from the firewall like it would have been.

 

I have had a bad master cylinder out of the box before. it happens.
If you are confident it bled out ok, try a new master without the deep bore, just to see if that 3/4" you adjusted was intended for a shallow piston? What is the worst that could happen, it doesn't work.

 

i actually did change masters,,,but still with the deep bore.

i'm wondering if i don't have some air still trapped in the lines or the master itself??? i was able to drive around the block,,,but not safely...super soft pedal that still goes to the floor,,,but now with a bit of resistance....

i'm about ready to cut holes in the floors and get my Flinstones on.....

 

I've always been told to bleed the furthest from the master first, then the second farthest, then second closest, then closest to be sure to get rid of all the air. It sounds like you started with the fronts. Just a thought.

 

second time around I did bleed from furthest to closest. finally got the rears to bleed out really well. same with the fronts. at least i thought i had.

 

are u positively sure ur master is bleed?i know there is the old school method of bleeding the master where u remove it and plum the 2 lines to the inside of the master and u pump till u c no bubbles.the new way is to plug those brake line ports on the master,fill it with brake fluid and pump the master till she gets hard as rock and won't travel any further.this way u know that there is no air trapped in tha mc.by doing the bleeding process the latter way,u don't have to remove the master ,and it will be bleed of all air. hope this helps. if u want to know how the master is bleed with the brake line ports pluged,that happens through the compensating port inside tha mc.

hope this helps

 

i bench bled the ever loving hell out of the master. never compressed it more than an inch, and continued until i had no more air and it was damn near impossible to move anymore. (did it with the plugs)

 

Another thing to consider - are the drums self adjusting? are the adjusters working if they are? or are they manual adjusting brakes that need to be adjusted. I have fought very similar problems and it turned out the brakes simply needed to be adjusted up. Just a thought.

 

you make a good point. they are self adjusting,,, but don't work that great. i did adjust them the second time around. made a small bit of difference.

 

Still nothing Erik? wtf?

If it was me, I'd try getting the front end up in the air, and cracking the rear bleeders to get a gravity bleed going. then i'd try fucking around with a longer plunger...if that was a no-go, then i'd shoot it.